Multivibrator control



Ce 9,' V VT BRAMAN 1,976,384

' MULTIVIBRATOR CONTROL Filed .April 26. 1929 INVENTOR V vem 'r. mmm

ATTORNE'Y FFECE Niwii- TATES- MULTIVIBRATR CONTROL Verne T. Braman, LongIsland City, N. Y., assignor to Radio Corporation of America, acorporation of Delaware Application Aprill26,, 1929, Serial No. 358,2872 claims. (oi. 250-436) The' present invention relates to synchronizingbe made therein in so far as such modifications systems, and isparticularly directed to a synfall Within the spiritand scope oftheipresent chronizing arrangement suitable for use in condisclosure asdefined by the hereinafter appendedir nection with facsim'le andtelevision systems,` claims. I

5l although it is to be recognizedthat theuse there- Now referring moreparticularly to the draw- 60 of is not restricted to such systems butthat the ing, I have llustrated a tuning fork 1 as being invention'm'aybe used for the purpose of synkof a substantially constant frequency andconchronizing two or more moving or vlbrating bodies trolled as to itsfrequency by means of a thermolocated at either adjacent or separatedpoints. stat control,` or other suitable control (not Further, theinvention relates to a method and shown), whereby the variations intemperature 65 `o means bywhich it is possible to apply a series oftending to change the frequency of the fork` arerelatively low frequencysynchronizing pulses for avoided, or the fork may be compensated as tothe purpose of synchronizing moving or vibratchanges in its frequencyby, .for example, forming v ing bodies located at different points. aportion of the fork of two distinct metals which Therefore, as an objectof my present invenhave different coeficients of expansion so that 70tion, I have sought to provide a method and thefork itself as itexpandsor contracts due to means by which moving or vibrating bodieslo-" temperature changes may be made to change theA cated at differentpoints may be synchronized, :frequency of the impressed impulses fordriving or by which synchronizing impulscs of a constant the same in anypreferred and desired manner.

Vfrequency may be applied for synchronizing mov- As a driving means for'the tuning fork 1, I -75 ing or vibrating bodies, such as synchronousmohave shown an electromagnetic driving system 3, tors, driving impulseWheels or La Cour wheels, which is driven by means of a vacuum tubeosordriving tuning forks of low vibrational fre- Gilla'bor upOh Which thefork freClU-BHCY impulse-S' quencies, or applied to any other well knownand are initially impressed through an electromagsuited Seg o neticpickup 7 associated with the fork 1. VIm- 80 As a further' objectof myinvention, I have pulses picked up by the pickup coil 'Z are.transsought to provide a method and means by which ferred throughv thePrimary Winding 11 Of the sub-harmonic frequencies may be produced fromtransformer 9 to the secondary winding 13 thereconstant frequencies. of,where they are impressed upon the grid mem- As a further object of myinvention, I have ber 17 of the oscillator 5, and across the circuit 85'sought to provide a multi-vibrator which may be including vthe gridmember 17, the biasing battery used as a means for splittingfrequencies, and 21 therefor, and the filament member 19. AS thusproducing 'fractional parts of the impressed shown, a source ofpotential 23 serves to provide frequencies, or, what has become known inthe heating Current for the filament member, and

'art as the sub-harmonics of a basic impressed the biasing battery 21with its negative terminal 90 frequency, connected towards the gridmember 17 provides a Still other objects of my invention are toproproper b'asng POtenal for the grid. Theoutduce,v in' a method to behereinafter set forth, an put Circuit Of the OSGllatOr 5 includes theplate arrangement suitable for applying synchronizing member 15 and thedrive coil 3, a source of plate 40 pulses to bodies which are to besynchronized, potential B+, WhiChintUrhS COImeGiBl thrugh 95 which issimple in its construction and arrangethe negative Source Of plateptenfial B- tO the ment of parts, a system Which is cheap andconfilament member 19. If desired, a meter for. venient to install; asystem which is eicient in measuring the plate output current necessary150 its use, and a system which can be readily set drive the fOrk may benserted in the plate Cirup and conveniently operated. cuit of the tube,as shown.

still other and further objects of my invention It is thus seen thatwhen once the fork 1 has will at once suggest themselves and becomeapbeen set into vibration impulses produced thereby parent to thoseskilled in the art to which the are transferred to the grid circuit ofthe oscillator invention relates by a reading of' the ,following 5,.andby amplification are then transferred to specification taken inconnection with the acthe drive means 3 for the purpose of keeping the.companying drawing, wherein, the single figure fork in vibration, andthe generated impulses from thereof shows a preferred form which mymventhe fork are in turn again picked up by the picktion may assume,although itis to be understood up coil '7 so as to continuously providea drive that the invention is not limited to the' construcmeans for thefork. For the purpose of keeping 55 tion illustrated, since variousmodifications may high frequency currents from the source of plate lteries 69 and 71.

element 73 which is connected .potential balance of the 'of each of thetubes 53 and potential B+, I have provided a choke coil 27, and shuntingthe source of plate potential B+ and B I have provided a by-passcondenser 25 for the purpose of passing the higher frequency currentsfrom the output circuit of the oscillator 5 back to the grid or inputcircuit.

Connected with the output circuit of tube 5 through a capacity coupling29, I have provided a further amplifying tube 31 whose grid member 33 isconnected with one side of the capacity coupling 29. The usual type ofgrid leak 41 connecting the grid 33, through a suitable source ofbiasing potential for the grid, and the filament member 37 at the tube31 has been provided for permitting electrons to leak off the grid andthus prevent blocking of the tube 31; Output energy from the tube 31flowing from the plate member 35, which is provided with asource ofplate potential from a source B+ connected through the choke coil 43 tokeep high'frequency potentials from the source of plate potential, isthen passed through a capacity coupling 45 and a resistance 47 to amulti-vibrator unit, including apair of vacuum tube oscillators 53 and55. In this connection, I have provided the resstor element 47, whichmay be variable where desired, for the purpose of adjusting theamplitude of the impulses supplied from the amplifier 31 to the vibratorunit.

The impulses transferred to the multi-vibrator unit includingoscillators 53 and 55 are superimposed upon the output of these tubesthrough resistances 49 and 51 respectively, and energy flowing from theplate members 57 and 59 of the tubes 53 and 55 will then be subjected toa series of superimposed impulses from the tuning fork 1. Each of thevacuum tubes 53 and 55, respectively, are provided with the usual gridmembers 61 and 63 and filament members 65 and 67, which are heated,respectively, by the usual heating bat- For the purpose of connectingthe tubes 53 and 55 of the multi-vibrator system together, so that onetube reacts upon the other, I have connected in the plate circuit,including the plate member 57, of the tube 53, a capacity with'V thegrid member 63 of the tube 55, and, similarly, to connect the plate 59of the tube 55 with the grid member 61 of the tube 53, I have provided aSimilar capacity element 75.

It will thus be seen when frequencies proportional to the frequency ofthe tuning fork 1 are impressed upon the multi-vibrator system,including the oscillators 53 and 55, that these ir'- pressed frequenciesfrom the fork change the vibrator system by changing the potential onboth the plate and grid members of each of the tubes 53 and 55, andthus, as will be seen from a consideration of the' drawing, since thevibrator system including the tubes 53 and 55 is in a most unstablecondition, the superimposed impulses originating from the fork 1 willtend to stabilize the vibrator system and cause it to vibrate at its ownnatural period. The natural period of the vibrator system is a functionof and is determined by the valves, of the resstor members 49 and 51,the capacity elements 73 and 75, and the resistors 77 and 83respectively, connected through a second set of variable resistors 79and 81 in the input circuit 55 respectively by a;V connection with thefilament members 65 and 67 thereof, as well as the tubes 53 and 55 whichmay be provided.

Suppose, for example, and for the purpose of as-i suming valves by whicha concrete illustration of operation may be given, that the vibratorsystem, including the oscillators 53 and 55, should have a naturalperiod of vibration of 100 cycles per second, then, due to the inherentunstable character of the vibrator, it will be readily seen that thisfrequency might change and vary between a pair of limiting values ofsay, for example, 95 to 105 cycles per second. Now, if we assume for thepurpose of further illustration that the fork 1 has a natural period ofvibration of 400 cycles per secondl, then, if the frequencycorresponding to the fork frequency is impressed upon the multi-vibratorsystem from the amplifier 31 through the capacity couplin'g and theresstor 47, to control the energy supplied-to the vibrator from thefork, it: will be seen that this impressed energy of the fork 1 tends tostabilize the vibrator system and cause it to vibrate continuously atits natural period. The natural period of vibration of the vibratorsystem may correspond to either the fork frequency, a harmonic thereof,ora subh'armonic thereof. In'the present case illustrated, it will berecognized, with the natural frequency of the vibrator system including.tubes 53'and 55 assumed to be 100 cycles, and the fork frequency assumedto be 400 cycles; that the vibrator system will maintain a steadyvibration at 100 cycles per second during periods when the forkfrequency is superimposed there'on. This frequency, according to theexample illustrated; is the fourth sub-harmonic or the quarter harmonic,of the natural fork frequency. Thus, a means for splitting frequeneiesand/or determining' sub-harmonics thereof which are constant has beenprovided.

Now, in order to further amplify the subharmonic frequency correspondingto the natural period ofv vibration of the muti-vibrator system, I haveprovided amplifying tubes 95' and 97, whose filament members 99 and 101ar'e connected inparallel with the'filament member's and 67 of thevibrator tubes 55 and 53. Each of tubes 95 and 97 have' their filamentmembers 99 and 101 heated from the sources of filament potentials 69 and71I respectively. The grid member 91 of the amplifier 95 is connectedwith the grid member 61 of the tube 53, and also with theplate member 59of the vibrator tube 55'by Way of the capacity element 75, andsimilarly, the grid member 93 of the amplifying tube 97 is connectedwith the grid member 63 of the vibrator tube 55, and also throughcapacity element '73 with the'plate' member 57 of the'vibratortube 53'.It will thus be seenl that energy from the'vibrator may readily betransferred'y to the; amplifying system, including, the tubes 95 and'97,and therein amplified, so that amplified energy fiowing from the platemembers 103 and 105 of the afmplifiers 95 and 97 respectively may bedirected through the c'oils 109 and' 1111 of thek relay member 107.ThroughA a common connectiony to a source of plate potential B+,potentials are suppliedl to platevmembers 1'03 and 105 of the tubes 95and 97. Thus, it will be seen that since the tubes 95 and 97 are'connected in push-pull fashion with the vibrators 53 and 55, thearmature 113 of the relay 107v will be caused to vibrate alternatelybetween contacts 115 and 117 respectively in accordance with whether ornot energy is being fed from the plate' member of the tube 95 or 97.

As has been shown by the: drawing, the armature 113 of the relay 107 isconnected through a contact point 1 19 to a point of zero potential, thecontact 115 is connected through a second contact member' 121 toia pointof negative pote'n- 150 tial, and, in a similar manner, the contact 117Vis connected through a contact point 123 with a source of positivepotential. Thus, as the armature 113 vibrates between the contacts 115and 1 1'7 at a frequency corresponding to the frequency of the vibratorsystem, current will alternatelyflow in the circuit including thecircuit connecting points 119 and 121, or the circuit including thecontacts 119 and 123. In either or both of these orcuits I have provideda second synchronizing member, which, for example, may be a 100 cycletuning fork, or any of the other forms of constant speed or periodsystems above mentioned.

Referring to' the above illustrated example for illustrating theprinciple of my invention, it will be readily seen that it is possibleto accurately drive from the output of either the circuit including thecontact 119 and 121, or the circuit including the contact 119 and 123, afork of a frequency of 100 cycles in an accurate manner. It has longbeen recognized in the prior art that it is most difiicult to accuratelydrive low frequency forks for the reason that the frequency thereof israther unstable and due to the fact that it is practically impossible toprovide a constant source of the desired frequency for applying drivingimpulses to a fork of low frequency in a manner similar `to that shownin connection with the drive of the fork l. A means has herein beenprovided whereby a relatively high frequency fork which can beconveniently controlled as to its frequency may be used to drive asecond fork of a lower frequency, or instead of a fork, an impulse or LaCour wheel, or a low frequency synchronous motor of any desired type orstyle.

As a means for keeping high frequency currents generated in the vibratorsystem including the tubes 53 and 55 from the source of plate potentialtherefor, I have provided a choke coil 125 in series with the source ofplate potential B+ for the oscillators 53 and 55 in a manner similar tothat shown in connection with the oscillator 5.

While the accompanying diagram shows the i supplying the desired platepotential to any of the vacuum tubes included in the system.

Other modifications of my invention than those herein disclosed will atonce suggest themselves and become apparent to those skilled in the artto which the invention relates by a reading of the hereinafter appendedclaims.

Having now described my invention, what I claim and desire to secure byLetters Patent is the following:

1. An energy transfer system comprising a source of .high frequencyenergy, a thermionic device serving as a low frequency unstableoscillator, a coupling tube connected between said high frequency sourceand said low frequency oscillator for transferring energy from said highfrequency source to said low frequency oscillator and for preventingreaction upon said high frequency source from said low frequencyoscillator, a therm'onic amplifying system having its input circuitconnected in parallel with the grid circuit of the low frequencyoscillator, and a load circuit connected with the output of saidamplifier.

2. A multi-vibrator unit comprising a pair of thermionic tubes havinginterconnected plate electrodes, a capacity connection between a gridelectrode of each tube and the plate electrode of the other tube,meansifor supplying energy of predetermined frequency to the circuitincluding the plate electrodes of each of the said pair of thermionictubes, a pair of push-pull amplifying tubes having the input electrodesthereof connected to the grid electrodes of the said first mentionedpair of tubes, and a load circuit oonnected with the output of saidpush-pull tubes.

VERNE T. BRAMAN.

